Is the number 1859 a prime number?

Answer 1

To find out if 1859 is a Prime number, use the rules of division:

• 1859 is not an even number, so it is not divisible by 2.
• The digits of 1859 add up to a number that is divisible by 3, so it is not divisible by 3.
• The last two digits (59) is not divisible by 4, so neither is 1859.
• The last digit is not 5, so it is not divisible by 5.
• 1859 is not divisible by 2 and it is not divisible by 3, so it is not divisible by 6.
• When you double the last digit (9 doubled is 18), and subtract that number from the rest of the number (859 - 18 = 841), if the answer is 0 or divisible by 7, the number itself is divisible by 7. If you can't readily tell if the number is divisible by 7, you can do the steps again. Starting with 841, doubling the 1 is still 1, so take 1 away from 84 to get 83. 83 is not divisible by 7, so neither is 1859.
• The last three digits (859) are not divisible by 8, so 1859 is not divisible by 8.
• If the sum of the digits is divisible by 9, the number is divisible by 9. The sum of the digits is 23, which is not divisible by 9.
• 1859 does not end with a 0, so it is not divisible by 10.
• If the sum of every second digit (8 + 9) minus the sum of the other digits (1 + 5) equals 0 or is divisible by 11, the number itself is divisible by 11. 17 - 6 = 11, so 1859 is divisible by 11.

Since 1859 is divisible by 11, it is a composite number (a number that has at least three factors: 1, the number itself, and at least one oher factor).